It is of the world-wide concern that as a result of rapid population increase, economical scale-up of developed countries, the industrialization of developing countries, the modernization of livelihood, and the rise of living standards, the consumption of food and energy resources is acceleratively increasing, and more environmental disruption occurs on the global scale. For the sustainable development in harmony with the environment, the widespread use of solar power generation and clean energy is desirable. Active research works have been made in this field.
With respect to the solar power generation, monocrystalline silicon solar batteries, polycrystalline silicon solar batteries, amorphous solar batteries, and compound solar batteries using cadmium telluride or indium copper selenide have been used in practice or become the major object of research and development. For the widespread use, problems including the manufacturing cost, the availability of source materials, and a long energy payback period must be solved. On the other hand, many solar batteries using organic materials intended for increasing the surface area and lowering the cost have also been proposed as disclosed in JP-A 131782/1978, 27387/1979, 35477/1980, 215070/1989, 10576/1992, and 85294/1994. They have the drawbacks of low efficiency conversion and poor durability.
Under the circumstances, Nature, Vol. 353, pp. 737-470, 1991, U.S. Pat. No. 4,927,721, 4,684,537, 5,084,365, 5,350,644, 5,463,057, 5,525,440, JP-A 249790/1995, JP-B 15097/1996 disclose photoelectric conversion devices comprising dye-sensitized nanoparticulate semiconductors (to be referred to as dye-sensitized photoelectric conversion device, hereinafter) as well as materials and processes for use in the manufacture of these converters. The device proposed in these patents is a wet solar battery having as a working electrode a porous titanium dioxide thin film spectrally sensitized with a ruthenium complex. A first advantage of this system is that photoelectric conversion devices are obtained at a relatively low cost since inexpensive oxide semiconductors can be used without a need for work-up to a high purity. A second advantage of this system is that since the dyes used have a broad absorption band, photons in almost all the wavelength band of visible light can be converted into electric current, achieving a high energy conversion efficiency of 10% (AM 1.5). However, since this device is a wet solar battery in which electrical connection with a counter electrode is provided by an electrolyte solution, long-term operation causes the depletion of the electrolyte solution and hence, a substantial drop of photoelectric conversion efficiency so that the device may not exert its own function. As a solution to these drawbacks, International Patent No. 93/20565 proposes a device using a solid electrolyte, JP-A 288142/1995, Solid State Tonics, 89 (1996), 263, and JP-A 27352/1997 propose a photoelectric conversion device using crosslinked polyethylene oxide solid polymer electrolyte for solidification, and J. Phys. Chem., 1995, 99, 1701-1703 proposes a photoelectric conversion device using polyacrylonitrile polymeric gel electrolyte for solidification. However, although the photoelectric conversion devices using these solid electrolytes are apparently solidified, most of them contain an electrolyte solution and thus cannot fundamentally avoid a drop of ion conductivity due to the depletion of the electrolytic solution and hence, a substantial decline of device performance. Therefore, engineers hesitate to say that the "depletion of electrolytic solution with the lapse of time" which is a problem inherent to wet solar batteries has been essentially solved.